Mercury vapor rectifying apparatus



June 14, 1949. s. G. KING 2,473,151

IERGURY VAPQUR RECTIFYING APPARATUS Filed July 24, 1945 Attorney Patented June 14, 1949 UNITED STATES ATENT QFFICE MERCURY VAPOR RECTIFYING APPARATUS Ohio Application July 24, 1945, Serial No. 606,817 In Great Britain May 22, 1944 Claims. 1

This invention relates to hot cathode mercury vapour rectifying apparatus. In such apparatus the storage of spare rectifier tubes is liable to present difiiculty since the tubes tend to deteriorate if left idle for long periods owing to poison ing of the cathode surfaces by the condensation of mercury vapour thereon. The result is that when the tube is put into service after this poisoning has taken place the anode-cathode voltage comes unduly high, and may rise above the critical ionisation voltage. This causes excessive bombardment of the cathode surface, and its destruction in a short time. The tube then ceases to function as a rectifier. When, therefore, tubes have not been used for long periods and such poisoning has occurred it is necessary to return them to the manufacturers for reconditioning. An object of the present invention is to eliminate the necessity for this.

According to the present invention hot cathode mercury vapour rectifying apparatus includes one or more spare mercury vapour rectifier tubes and means controlled by the operation of the equ pment for intermittently passing currents through the anode and filament circuits of the spare tubes.

For example the spare tubes may be energised every time the equipment is switched on and automatically switched off after they have been switched on for a predetermined period.

The circuit arrangements of the spare tubes may include any convenient timing equipment but one particular embodiment of the invention is shown diagrammatically in the accompanying drawing.

In the arrangement shown A and A represent main conductors from which the main hot cathode mercury vapour rectifying apparatus is fed. The main hot cathode mercury vapour rectifying apparatus consists of a transformer T whose primary T is fed from the main conductors A and A and whose secondaries T and T respectively supply the excitation to the main tubes V at their corresponding anodes V and filaments V The load on the main apparatus is designated by W. The apparatus embodying the present invention comprises a time switch A for example of known type, hereinafter termed the starting switch, arranged to be closed for a short period whenever the main apparatus is switched on. The starting switch A closes the circuit of a relay B which in turn closes contacts B 13 and B The contacts B are arranged in parallel with the switch A and in series with the contacts C of a further relay C the contacts of which are normally closed. Thus when the starting switch A has been closed the relay B will be held closed through its contacts B even after the switch A opens until such time as the energisation of the relay C breaks its contacts C The relay B, by closing the contacts B also brings the primary of a transformer B into cir cult. This transformer has two seconda es D and D One of these secondaries 13 se to heat the filaments E of the one or more spare hot cathode mercury vapour tubes E as shown while the other supplies heating current to the heating element of a switch F which is of the thermal delay time type such that after an interval it closes and thereby energises a relay F to close its contacts F Since the contacts 13 have already been closed by the relay B it will be seen that closing of the contacts F brings into circuit the primary G of a transformer G.

The secondary G of the transformer G is connected as shown to the anodes P3- of the spare tubes E so as to load them and is also connected at its midpoint to one end of a resistance H, the other end of which is connected to the filament circuits of the spare tubes E. The resistance H is thus subject to a direct current potential acts as a loading resistance to determine the value of the current passed through the tubes E in accordance with their rating. The direct current potential applied to the resistance 1-! also applied across a resistance and capacit network J which includes the energising circuit of the relay C and is of a well known type for obtaining a time delay comprising a resistance J condenser K and a neon tube L, the arrangement being such that voltage is built up the;

til it is sufiicient to cause the neon tube L to sm he whereupon the instantaneous current thus ing operates the relay C and hence opens contacts C v It will be seen that the opening of the contacts C trips the relay B so as to open the contac B B B and hence deenergise the transfcrne D and G so that the circuit is rendered inopera L. but is ready for operation in a similar manner to that described above when the starting switch 3 A is again closed. It will be appreciated that if the voltage required by the filaments E and the heating filament or like element of the switch F is the same, the transformer D could have a single secondar connected to all three filaments.

Further, it will be readily understood that the details of the circuit employed may be varied considerably within the terms of the appended claims without departing from this invention.

What I claim as my invention and desire to secure by Letters Patent is:

1. Hot cathode mercury vapour rectifying apparatus including at least one operative mercury vapor rectifier tube in a main circuit, at least one spare mercury vapor rectifier tube, auxiliary apparatus controlled by the operation of the equipment whereby currents can be caused to pass through the anode and filament circuits. of the said spare tube, and a time switch which is automatically closed when the rectifying apparatus is switched on and opens automatically to switch the auxiliary apparatus off after a predetermined period.

2. Hot cathode mercury vapour rectifying apparatus including at least one operative mercury vapour rectifier tube, at least one spare mercury vapour rectifier tube, means whereby currents can be caused to pass through the anode and filament circuits of the said spare tube comprising separate transformers for supplying the c 'rrent respectively to the filament and anode circuits of the spare tube, an initiating switch which on switching on the main apparatus closes the circuit of the transformer feeding the filament circuit of the spare tube, a time switch the closing of which is initiated by the closing of the initiating switch and which closes the circuit of the former feeding the anode after an interval sufficient to enable the filament of the spare tube to have warmed up, and time apparatus for opening the initiating switch after a predetermined period.

3. Hot cathode mercury vapour rectifying apparatus as claimed in claim 1 including a relay for switching off the anode and filament circuits of the spare tube as by opening the initiating switch, the relay being controlled by a circuit including a neon or like discharge tube and a condenser which is charged by the current passing to at least one of the circuits of the spare tubes until the neon tube strikes causing operation of the relay.

4. Hot cathode mercury vapour rectifying apparatus as claimed in claim 10, including means whereby the anode circuit of each spare mercury vapour rectifier tube is maintained under a predetermined load during the passage of current therethrough.

5. Hot cathode mercury vapour rectifying apparatus including at least one operative mercury vapour rectifier tube, at least one spare mercury vapour rectifier tube, and means for passing current through the said spare mercury vapour rectifier tube comprising a starting switch arranged to be closed for a short period when the main apparatus is brought into operation, an initiating relay controlled by the starting switch and closing not only a holding circuit for the starting switch in which a cut-out relay switch is also arranged, but also the primary circuit of a filament current transformer which supplies current to the filament of the spare tube and to a delayed action time switch controlling the primary circuit of an anode current transformer for supplying current to the anode circuit of the spare tube,

4 which anode circuit is also controlled by the initiation switch, and time apparatus controlled by current from the anode current transformer for operating the cut-out relay switch after a predetermined time interval so as to break the control circuit of the initiating switch which then returns the apparatus to its inoperative condition.

6. Hot cathode rectifying apparatus including at least one operative rectifier tube in a main circuit, at least one spare rectifier tube, and means for energizing said spare tube for predetermined periods of time, whereby lack of use of said tube for prolonged periods does not materially affect the characteristics of the tube, said means including apparatus actuated upon the happening of a predetermined event to energize at least the filament circuit of said spare tube and other means for de-energizing said circuit after said predetermined period of time.

7. Hot cathode rectifying apparatus including at least one operative rectifier tube in a main circuit, at least one spare rectifier tube, and means for energizing said spare tube for predetermined periods of time, whereby lack of use of said tube for prolonged periods does not materially afiect the characteristics of the tube, said means including apparatus actuated upon the happening of a predetermined event to energize the filament and anode circuits of said spare tube and other means for de-energizing said circuit after said predetermined period of time.

8. Hot cathode mercury vapor rectifying apparatus including at least one operative mercury vapor rectifier tube, at least one spare mercury vapor rectifier tube, means whereby currents can be caused to pass through the anode and filament circuits of the said spare tube comprising separate transformers for supplying the current respectively to the filament and anode circuits of the spare tube, an initiating switch which on the happening of a predetermined event closes the circuit of the transformer feeding the filament circuit of the spare tube, a time switch the closing of which is initiated by the closing of the initiating switch and which closes the circuit of the transformer feeding the anode after an interval sufficient to enable the filament of the spare tube to have warmed up, and time apparatus for opening the initiating switch after a predetermined period.

9. Hot cathode rectifying apparatus including at least one operative rectifier tube in a main circuit, at least one spare rectifier tube, and means for energizing said spare tube for predetermined periods of time, whereby lack of use of said tube for prolonged periods does not materially affect the characteristics of the tube, said means including apparatus controlled by the operation of the equipment for passing currents through the anode and filament circuits of the spare tube for limited periods and other means for de-energizing said circuit after said predetermined period of time.

10. Hot cathode mercury vapor rectifying apparatus including at least one operative mercury vapor rectifier tube in a main circuit, at least one spare mercury vapor rectifying tube, and means for energizing said spare tube for predetermined periods of time, whereby lack of use of said tube for prolonged periods does not materially affect the characteristics of the tube, said means including apparatus actuated when a rectifier tube in said main circuit is energized whereby currents are caused to pass through the anode and filament circuits of the spare tube and other means for dis-energizing said circuit after said 6 UNITED STATES PATENTS Name Date Stone Aug. 7, 1934 ODonovan Apr. 9, 1935 Wright Dec. 10, 1935 Stone Dec. 17, 1935 Beetem Feb. 9, 1937 Whitesell Apr. 3, 1945 

